Image textures with transparancy Help
In Blender transparent areas are not rendered as checkers... if you converted a jpeg that had checkered background to png, that does not make checkered areas transparent!! Your png has no transparency, I feel, this is why the checkers are always there...

You should either download that image again, but directly in a format that supports transparency (like png) or convert the checkered part of the png to a true transparent area...

In Blender if an image has supposedly transparent areas completely black or white, you can tell it to use those absolute colors to get transparency  (that is the purpose of "calculate" and "invert" options in the image texture  "image sampling" panel). "calculate" uses blacks in image to represent transparency, "invert" makes "calculate" use whites. 

This assumes your material and texture are set to be transparent, and the texture has some influence (>0) on material transparency.